cutils: add popcount/popcountl/popcountll static inline definitions

Just pass them through to their specific GCC builtins. If we find
that the builtins are not performing well or have other issues, we can
pull in existing public implementations and/or write arch-specific
helpers if necessary.

Change-Id: I278e6b73d75fac88808ed4546070d288c06f79e0
Signed-off-by: Dima Zavin <dima@android.com>

include/cutils/bitops.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __CUTILS_BITOPS_H
+#define __CUTILS_BITOPS_H
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+static inline int popcount(unsigned int x)
+{
+    return __builtin_popcount(x);
+}
+
+static inline int popcountl(unsigned long x)
+{
+    return __builtin_popcountl(x);
+}
+
+static inline int popcountll(unsigned long long x)
+{
+    return __builtin_popcountll(x);
+}
+
+__END_DECLS
+
+#endif /* __CUTILS_BITOPS_H */